Originally Posted by edwinm3
ASA blowers use a centrifugal clutch. They're very good and it's what I had on my e46. Don't think anybody is using them on E9X applications. Very good and expensive. Torque you feel at low rpms
G-Power, who exclusively uses ASA superchargers, retain the centrifugal clutch on all their current supercharger kits; including the E9X M3 kits.
I'll grab a picture of an install we're doing at the shop and take the pulley off the blower to show some detail.